package org.bouncycastle.asn1.x509;

import org.bouncycastle.asn1.ASN1Encodable;
import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.ASN1TaggedObject;
import org.bouncycastle.asn1.DEREncodable;
import org.bouncycastle.asn1.DERObject;
import org.bouncycastle.asn1.DERObjectIdentifier;
import org.bouncycastle.asn1.DERSequence;

public class AlgorithmIdentifier extends ASN1Encodable {
    private DERObjectIdentifier objectId;
    private DEREncodable parameters;
    private boolean parametersDefined = false;

    public static AlgorithmIdentifier getInstance(ASN1TaggedObject obj, boolean explicit) {
        return getInstance(ASN1Sequence.getInstance(obj, explicit));
    }

    public static AlgorithmIdentifier getInstance(Object obj) {
        if (obj == null || obj instanceof AlgorithmIdentifier) {
            return (AlgorithmIdentifier) obj;
        }

        if (obj instanceof DERObjectIdentifier) {
            return new AlgorithmIdentifier((DERObjectIdentifier) obj);
        }

        if (obj instanceof String) {
            return new AlgorithmIdentifier((String) obj);
        }

        if (obj instanceof ASN1Sequence) {
            return new AlgorithmIdentifier((ASN1Sequence) obj);
        }

        throw new IllegalArgumentException("unknown object in factory");
    }

    public AlgorithmIdentifier(DERObjectIdentifier objectId) {
        this.objectId = objectId;
    }

    public AlgorithmIdentifier(String objectId) {
        this.objectId = new DERObjectIdentifier(objectId);
    }

    public AlgorithmIdentifier(DERObjectIdentifier objectId, DEREncodable parameters) {
        parametersDefined = true;
        this.objectId = objectId;
        this.parameters = parameters;
    }

    public AlgorithmIdentifier(ASN1Sequence seq) {
        if (seq.size() < 1 || seq.size() > 2) {
            throw new IllegalArgumentException("Bad sequence size: " + seq.size());
        }

        objectId = DERObjectIdentifier.getInstance(seq.getObjectAt(0));

        if (seq.size() == 2) {
            parametersDefined = true;
            parameters = seq.getObjectAt(1);
        } else {
            parameters = null;
        }
    }

    public DERObjectIdentifier getObjectId() {
        return objectId;
    }

    public DEREncodable getParameters() {
        return parameters;
    }

    /**
     * Produce an object suitable for an ASN1OutputStream.
     * 
     * <pre>
     *      AlgorithmIdentifier ::= SEQUENCE {
     *                            algorithm OBJECT IDENTIFIER,
     *                            parameters ANY DEFINED BY algorithm OPTIONAL }
     * </pre>
     */
    public DERObject toASN1Object() {
        ASN1EncodableVector v = new ASN1EncodableVector();

        v.add(objectId);

        if (parametersDefined) {
            v.add(parameters);
        }

        return new DERSequence(v);
    }
}
